Effect of wetting–drying cycles on the desiccation of tailings pre-dewatered with super absorbent polymer

The main objective of this investigation is to understand the desiccation behaviour of fluid fine tailings (FFT) pre-dewatered with a superabsorbent polymer (SAP) with respect to wetting–drying cycles. Raw FFT (control) and pre-dewatered FFT with SAP were subjected to five cycles of wetting and six cycles of drying. Evaporation was found to be the dominant mechanism in the dewatering of raw FFT, as well as FFT pre-dewatered with SAP. In both cases, the suction developed in each drying cycle was eliminated temporarily by the succeeding wetting cycle. The minimum solids content within the column was found to be around 70%, which corresponded to a vane shear strength of 4.5 kPa. Based on the digital images of the surface, the crack intensity factors of the raw FFT and pre-dewatered FFT were calculated to be 26 and 14%, respectively. Scanning electron microscopy and mercury intrusion porosimetry analyses indicated that the FFT pre-dewatered with SAP after 25 days of evaporation in the second lift exhibited the most compacted texture. The solids content of the FFT pre-dewatered with SAP increased to 98% from an initial 50%. The SAP pre-dewatering method can significantly increase the shear strength of FFT subjected to wetting–drying cycles.